Optical lens set

ABSTRACT

An optical lens set includes no air gap between the first lens element and the second lens element, the third lens element of a concave object-side surface near its optical-axis, and the sixth lens element of a convex image-side surface near its periphery. The Abbe number ν3 of the third lens element and the Abbe number ν5 of the fifth lens element satisfy |ν3−ν5|≤25.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Chinese patent application No.201610947936.4, filed on Nov. 2, 2016. The contents of which are herebyincorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens setfor use in taking pictures and in recording videos. Specificallyspeaking, the present invention is directed to an optical imaging lensset for use in mobile phones, in cameras, in tablet personal computers,or in personal digital assistants (PDA) to take pictures and to recordvideos.

2. Description of the Prior Art

In recent years, the popularity of mobile phones and digital camerasmakes the sizes of various portable electronic products reduce quickly,and so does those of the photography modules to meet the demands. Thecurrent trend of research is to develop an optical imaging lens set of ashorter total length with uncompromised good imaging quality. However,good and necessary optical properties, such as the system aberrationimprovement, as well as production cost and production feasibilityshould be taken into consideration, too.

As far as an optical imaging lens set of six lens elements is concerned,currently the distance between an object-side surface of the first lenselement to an image plane, namely the total length TTL of an opticalimaging lens set, is too long to shrink mobile phones and digitalcameras. The designing of the optical lens is not just scaling down theoptical lens which has good optical performance, but also needs toconsider the material characteristics and satisfy some practicalrequirements like assembly yield.

Accordingly, it is more difficult to diminish a mini-lens than todiminish a conventional lens. Therefore, how to reduce the total lengthof a photographic device, but still maintain good optical performanceunder dim light background, is an important objective to research.

SUMMARY OF THE INVENTION

In light of the above, the present invention proposes an optical imaginglens set of six lens elements that is smaller in total length,technically possible, has low flare and good optical performance. Theoptical imaging lens set of six lens elements of the present inventionfrom an object side toward an image side in order along an optical axishas a first lens element, a second lens element, a third lens element, afourth lens element, a fifth lens element and a sixth lens element. Eachlens element has an object-side surface facing toward an object side aswell as an image-side surface facing toward an image side. The opticalimaging lens set exclusively has the first lens element, the second lenselement, the third lens element, the fourth lens element, the fifth lenselement and the sixth lens element with refractive power.

There is no air gap disposed between the first lens element and thesecond lens element. The third lens element has an object-side surfacewith a concave portion in a vicinity of the optical axis. The sixth lenselement has an image-side surface with a convex portion in a vicinity ofits periphery. An Abbe number ν3 of the third lens element and an Abbenumber ν5 of the fifth lens element satisfy |ν3−ν5|≤25.

In the optical imaging lens set of six lens elements of the presentinvention, the second lens element has a second lens element thicknessT₂ along the optical axis and the third lens element has a third lenselement thickness T₃ along the optical axis to satisfy T₃/T₂≤2.7.

In the optical imaging lens set of six lens elements of the presentinvention, EFL is an effective focal length of the optical imaging lensset, an air gap G₃₄ between the third lens element and the fourth lenselement along the optical axis and an air gap G₅₅ between the fifth lenselement and the sixth lens element along the optical axis to satisfyEFL/(G₃₄+G₅₆)≤42.3.

In the optical imaging lens set of six lens elements of the presentinvention, the fifth lens element has a fifth lens element thickness T₅along the optical axis to satisfy T₅/(G₃₄+G₅₆)≤6.

In the optical imaging lens set of six lens elements of the presentinvention, BFL is a distance between the image-side surface of the sixthlens element and an image plane along the optical axis to satisfyBFL/(G₃₄+G₅₆)≤8.1.

The optical imaging lens set of six lens elements of the presentinvention satisfies T₂/G₅₆≤1.8.

In the optical imaging lens set of six lens elements of the presentinvention, a sum of all air gaps AAG between each lens elements from thefirst lens element to the sixth lens element along the optical axissatisfies AAG/G₅₆≤9.1.

In the optical imaging lens set of six lens elements of the presentinvention, the sixth lens element has a sixth lens element thickness T₆along the optical axis to satisfy EFL/T₆≤11.7.

In the optical imaging lens set of six lens elements of the presentinvention, the first lens element has a first lens element thickness T₁along the optical axis and an air gap G₄₅ between the fourth lenselement and the fifth lens element along the optical axis to satisfyT₁/G₄₅≤6.6.

In the optical imaging lens set of six lens elements of the presentinvention, ALT is a total thickness of all six lens elements and thefourth lens element has a fourth lens element thickness T₄ along theoptical axis to satisfy ALT/T₄≤13.1.

The optical imaging lens set of six lens elements of the presentinvention satisfies EFL/BFL≤4.9.

The optical imaging lens set of six lens elements of the presentinvention satisfies T₆/T₄≤2.4.

In the optical imaging lens set of six lens elements of the presentinvention, TTL is a distance from the object-side surface of the firstlens element to an image plane to satisfy TTL/AAG≤6.1.

The optical imaging lens set of six lens elements of the presentinvention satisfies ALT/T₆≤6.9.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₂₃ between the second lens element and the thirdlens element along the optical axis satisfies T₁/G₂₃≤2.2.

In the optical imaging lens set of six lens elements of the presentinvention, TL is a distance between the object-side surface of the firstlens element and the image-side surface of the sixth lens element alongthe optical axis to satisfy TTL/TL≤1.4.

The optical imaging lens set of six lens elements of the presentinvention satisfies TL/T₄≤17.2.

The optical imaging lens set of six lens elements of the presentinvention satisfies BFL/T₆≤2.6.

The optical imaging lens set of six lens elements of the presentinvention satisfies ALT/BFL≤3.5.

The optical imaging lens set of six lens elements of the presentinvention satisfies EFL/G₂₃≤8.7.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrates the methods for determining the surface shapes andfor determining one region is a region in a vicinity of the optical axisor the region in a vicinity of its circular periphery of one lenselement.

FIG. 6 illustrates a first example of the optical imaging lens set ofthe present invention.

FIG. 7A illustrates the longitudinal spherical aberration on the imageplane of the first example.

FIG. 7B illustrates the astigmatic aberration on the sagittal directionof the first example.

FIG. 7C illustrates the astigmatic aberration on the tangentialdirection of the first example.

FIG. 7D illustrates the distortion aberration of the first example.

FIG. 8 illustrates a second example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the imageplane of the second example.

FIG. 9B illustrates the astigmatic aberration on the sagittal directionof the second example.

FIG. 9C illustrates the astigmatic aberration on the tangentialdirection of the second example.

FIG. 9D illustrates the distortion aberration of the second example.

FIG. 10 illustrates a third example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the imageplane of the third example.

FIG. 11B illustrates the astigmatic aberration on the sagittal directionof the third example.

FIG. 11C illustrates the astigmatic aberration on the tangentialdirection of the third example.

FIG. 11D illustrates the distortion aberration of the third example.

FIG. 12 illustrates a fourth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the imageplane of the fourth example.

FIG. 13B illustrates the astigmatic aberration on the sagittal directionof the fourth example.

FIG. 13C illustrates the astigmatic aberration on the tangentialdirection of the fourth example.

FIG. 13D illustrates the distortion aberration of the fourth example.

FIG. 14 illustrates a fifth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the imageplane of the fifth example.

FIG. 15B illustrates the astigmatic aberration on the sagittal directionof the fifth example.

FIG. 15C illustrates the astigmatic aberration on the tangentialdirection of the fifth example.

FIG. 15D illustrates the distortion aberration of the fifth example.

FIG. 16 illustrates a sixth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the imageplane of the sixth example.

FIG. 17B illustrates the astigmatic aberration on the sagittal directionof the sixth example.

FIG. 17C illustrates the astigmatic aberration on the tangentialdirection of the sixth example.

FIG. 17D illustrates the distortion aberration of the sixth example.

FIG. 18 illustrates a seventh example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the imageplane of the seventh example.

FIG. 19B illustrates the astigmatic aberration on the sagittal directionof the seventh example.

FIG. 19C illustrates the astigmatic aberration on the tangentialdirection of the seventh example.

FIG. 19D illustrates the distortion aberration of the seventh example.

FIG. 20 illustrates an eighth example of the optical imaging lens set ofsix lens elements of the present invention.

FIG. 21A illustrates the longitudinal spherical aberration on the imageplane of the eighth example.

FIG. 21B illustrates the astigmatic aberration on the sagittal directionof the eighth example.

FIG. 21C illustrates the astigmatic aberration on the tangentialdirection of the eighth example.

FIG. 21D illustrates the distortion aberration of the eighth example.

FIG. 22 shows the optical data of the first example of the opticalimaging lens set.

FIG. 23 shows the aspheric surface data of the first example.

FIG. 24 shows the optical data of the second example of the opticalimaging lens set.

FIG. 25 shows the aspheric surface data of the second example.

FIG. 26 shows the optical data of the third example of the opticalimaging lens set.

FIG. 27 shows the aspheric surface data of the third example.

FIG. 28 shows the optical data of the fourth example of the opticalimaging lens set.

FIG. 29 shows the aspheric surface data of the fourth example.

FIG. 30 shows the optical data of the fifth example of the opticalimaging lens set.

FIG. 31 shows the aspheric surface data of the fifth example.

FIG. 32 shows the optical data of the sixth example of the opticalimaging lens set.

FIG. 33 shows the aspheric surface data of the sixth example.

FIG. 34 shows the optical data of the seventh example of the opticalimaging lens set.

FIG. 35 shows the aspheric surface data of the seventh example.

FIG. 36 shows the optical data of the eighth example of the opticalimaging lens set.

FIG. 37 shows the aspheric surface data of the eighth example.

FIG. 38 shows some important ratios in the examples.

DETAILED DESCRIPTION

Before the detailed description of the present invention, the firstthing to be noticed is that in the present invention, similar (notnecessarily identical) elements are labeled as the same numeralreferences. In the entire present specification, “a certain lens elementhas negative/positive refractive power” refers to the part in a vicinityof the optical axis of the lens element has negative/positive refractivepower calculated by Gaussian optical theory. An object-side/image-sidesurface refers to the region which allows imaging light passing through,in the drawing, imaging light includes Lc (chief ray) and Lm (marginalray). As shown in FIG. 1, the optical axis is “I” and the lens elementis symmetrical with respect to the optical axis I. The region A thatnear the optical axis and for light to pass through is the region in avicinity of the optical axis, and the region C that the marginal raypassing through is the region in a vicinity of a certain lens element'scircular periphery. In addition, the lens element may include anextension part E for the lens element to be installed in an opticalimaging lens set (that is the region outside the region C perpendicularto the optical axis). Ideally speaking, no light would pass through theextension part, and the actual structure and shape of the extension partis not limited to this and may have other variations. For the reason ofsimplicity, the extension part is not illustrated in the followingexamples. More, precisely, the method for determining the surface shapesor the region in a vicinity of the optical axis, the region in avicinity of its circular periphery and other regions is described in thefollowing paragraphs:

1. FIG. 1 is a radial cross-sectional view of a lens element. Beforedetermining boundaries of those aforesaid portions, two referentialpoints should be defined first, middle point and conversion point. Themiddle point of a surface of a lens element is a point of intersectionof that surface and the optical axis. The conversion point is a point ona surface of a lens element, where the tangent line of that point isperpendicular to the optical axis. Additionally, if multiple conversionpoints appear on one single surface, then these conversion points aresequentially named along the radial direction of the surface withnumbers starting from the first conversion point. For instance, thefirst conversion point (closest one to the optical axis), the secondconversion point, and the N^(th) conversion point (farthest one to theoptical axis within the scope of the clear aperture of the surface). Theportion of a surface of the lens element between the middle point andthe first conversion point is defined as the portion in a vicinity ofthe optical axis. The portion located radially outside of the N^(th)conversion point (but still within the scope of the clear aperture) isdefined as the portion in a vicinity of a periphery of the lens element.In some embodiments, there are other portions existing between theportion in a vicinity of the optical axis and the portion in a vicinityof a periphery of the lens element; the numbers of portions depend onthe numbers of the conversion point(s). In addition, the radius of theclear aperture (or a so-called effective radius) of a surface is definedas the radial distance from the optical axis I to a point ofintersection of the marginal ray Lm and the surface of the lens element.

2. Referring to FIG. 2, determining the shape of a portion is convex orconcave depends on whether a collimated ray passing through that portionconverges or diverges. That is, while applying a collimated ray to aportion to be determined in terms of shape, the collimated ray passingthrough that portion will be bended and the ray itself or its extensionline will eventually meet the optical axis. The shape of that portioncan be determined by whether the ray or its extension line meets(intersects) the optical axis (focal point) at the object-side orimage-side. For instance, if the ray itself intersects the optical axisat the image side of the lens element after passing through a portion,i.e. the focal point of this ray is at the image side (see point R inFIG. 2), the portion will be determined as having a convex shape. On thecontrary, if the ray diverges after passing through a portion, theextension line of the ray intersects the optical axis at the object sideof the lens element, i.e. the focal point of the ray is at the objectside (see point M in FIG. 2), that portion will be determined as havinga concave shape. Therefore, referring to FIG. 2, the portion between themiddle point and the first conversion point has a convex shape, theportion located radially outside of the first conversion point has aconcave shape, and the first conversion point is the point where theportion having a convex shape changes to the portion having a concaveshape, namely the border of two adjacent portions. Alternatively, thereis another common way for a person with ordinary skill in the art totell whether a portion in a vicinity of the optical axis has a convex orconcave shape by referring to the sign of an “R” value, which is the(paraxial) radius of curvature of a lens surface. The R value iscommonly used in conventional optical design software such as Zemax andCodeV. The R value usually appears in the lens data sheet in thesoftware. For an object-side surface, positive R means that theobject-side surface is convex, and negative R means that the object-sidesurface is concave. Conversely, for an image-side surface, positive Rmeans that the image-side surface is concave, and negative R means thatthe image-side surface is convex. The result found by using this methodshould be consistent as by using the other way mentioned above, whichdetermines surface shapes by referring to whether the focal point of acollimated ray is at the object side or the image side.

3. For none conversion point cases, the portion in a vicinity of theoptical axis is defined as the portion between 0˜50% of the effectiveradius (radius of the clear aperture) of the surface, whereas theportion in a vicinity of a periphery of the lens element is defined asthe portion between 50˜100% of effective radius (radius of the clearaperture) of the surface.

Referring to the first example depicted in FIG. 3, only one conversionpoint, namely a first conversion point, appears within the clearaperture of the image-side surface of the lens element. Portion I is aportion in a vicinity of the optical axis, and portion II is a portionin a vicinity of a periphery of the lens element. The portion in avicinity of the optical axis is determined as having a concave surfacedue to the R value at the image-side surface of the lens element ispositive. The shape of the portion in a vicinity of a periphery of thelens element is different from that of the radially inner adjacentportion, i.e. the shape of the portion in a vicinity of a periphery ofthe lens element is different from the shape of the portion in avicinity of the optical axis; the portion in a vicinity of a peripheryof the lens element has a convex shape.

Referring to the second example depicted in FIG. 4, a first conversionpoint and a second conversion point exist on the object-side surface(within the clear aperture) of a lens element. In which portion I is theportion in a vicinity of the optical axis, and portion III is theportion in a vicinity of a periphery of the lens element. The portion ina vicinity of the optical axis has a convex shape because the R value atthe object-side surface of the lens element is positive. The portion ina vicinity of a periphery of the lens element (portion III) has a convexshape. What is more, there is another portion having a concave shapeexisting between the first and second conversion point (portion II).

Referring to a third example depicted in FIG. 5, no conversion pointexists on the object-side surface of the lens element. In this case, theportion between 0˜50% of the effective radius (radius of the clearaperture) is determined as the portion in a vicinity of the opticalaxis, and the portion between 50˜100% of the effective radius isdetermined as the portion in a vicinity of a periphery of the lenselement. The portion in a vicinity of the optical axis of theobject-side surface of the lens element is determined as having a convexshape due to its positive R value, and the portion in a vicinity of aperiphery of the lens element is determined as having a convex shape aswell.

As shown in FIG. 6, the optical imaging lens set 1 of six lens elementsof the present invention, sequentially located from an object side 2(where an object is located) to an image side 3 along an optical axis 4,has an aperture stop (ape. stop) 80, a first lens element 10, a secondlens element 20, a third lens element 30, a fourth lens element 40, afifth lens element 50, a sixth lens element 60, a filter 70 and an imageplane 71. Generally speaking, the first lens element 10, the second lenselement 20, the third lens element 30, the fourth lens element 40, thefifth lens element 50 and the sixth lens element 60 may be made of atransparent plastic material but the present invention is not limited tothis, and each has an appropriate refractive power. There areexclusively six lens elements, which means the first lens element 10,the second lens element 20, the third lens element 30, the fourth lenselement 40, the fifth lens element 50 and the sixth lens element 60,with refractive power in the optical imaging lens set 1 of the presentinvention. The optical axis 4 is the optical axis of the entire opticalimaging lens set 1, and the optical axis of each of the lens elementscoincides with the optical axis of the optical imaging lens set 1.

Furthermore, the optical imaging lens set 1 includes an aperture stop(ape. stop) 80 disposed in an appropriate position. In FIG. 6, theaperture stop 80 is disposed between the object side 2 and the firstlens element 10. When light emitted or reflected by an object (notshown) which is located at the object side 2 enters the optical imaginglens set 1 of the present invention, it forms a clear and sharp image onthe image plane 71 at the image side 3 after passing through theaperture stop 80, the first lens element 10, the second lens element 20,the third lens element 30, the fourth lens element 40, the fifth lenselement 50, the sixth lens element 60 and the filter 70. In oneembodiments of the present invention, the optional filter 70 may be afilter of various suitable functions, for example, the filter 70 may bean infrared cut filter (IR cut filter), placed between the image-sidesurface 62 of the sixth lens element 60 and the image plane 71.

Each lens element in the optical imaging lens set 1 of the presentinvention has an object-side surface facing toward the object side 2 aswell as an image-side surface facing toward the image side 3. Forexample, the first lens element 10 has an object-side surface 11 and animage-side surface 12; the second lens element 20 has an object-sidesurface 21 and an image-side surface 22; the third lens element 30 hasan object-side surface 31 and an image-side surface 32; the fourth lenselement 40 has an object-side surface 41 and an image-side surface 42;the fifth lens element 50 has an object-side surface 51 and animage-side surface 52; the sixth lens element 60 has an object-sidesurface 61 and an image-side surface 62. In addition, each object-sidesurface and image-side surface in the optical imaging lens set 1 of thepresent invention has a part (or portion) in a vicinity of its periphery(circular periphery part) away from the optical axis 4 as well as a partin a vicinity of the optical axis (optical axis part) close to theoptical axis 4.

Each lens element in the optical imaging lens set 1 of the presentinvention further has a central thickness T on the optical axis 4. Forexample, the first lens element 10 has a first lens element thicknessT₁, the second lens element 20 has a second lens element thickness T₂,the third lens element 30 has a third lens element thickness T₃, thefourth lens element 40 has a fourth lens element thickness T₄, the fifthlens element 50 has a fifth lens element thickness T₅, the sixth lenselement 60 has a sixth lens element thickness T₅. Therefore, the totalthickness of all the lens elements in the optical imaging lens set 1along the optical axis 4 is ALT=T₁+T₂+T₃+T₄+T₅+T₆.

In addition, between two adjacent lens elements in the optical imaginglens set 1 of the present invention there may be an air gap along theoptical axis 4. For example, there is no air gap G₁₂ disposed betweenthe first lens element 10 and the second lens element 20 so G₁₂ is 0.There is an air gap G₂₃ is disposed between the second lens element 20and the third lens element 30, an air gap G₃₄ is disposed between thethird lens element 30 and the fourth lens element 40, an air gap G₄₅ isdisposed between the fourth lens element 40 and the fifth lens element50 as well as an air gap G₅₆ is disposed between the fifth lens element50 and the sixth lens element 60. Therefore, the sum of total four airgaps between adjacent lens elements from the first lens element 10 tothe sixth lens element 60 along the optical axis 4 isAAG=G₂₃+G₃₄+G₄₅+G₅₆.

In addition, the distance from the object-side surface 11 of the firstlens element 10 to the image-side surface 62 of the sixth lens element60 along the optical axis 4 is TL. The distance between the object-sidesurface 11 of the first lens element 10 to the image plane 71, namelythe total length of the optical imaging lens set along the optical axis4 is TTL; the effective focal length of the optical imaging lens set isEFL; the distance between the image-side surface 62 of the sixth lenselement 60 and the image plane 71 along the optical axis 4 is BFL.

Furthermore, the focal length of the first lens element 10 is f1; thefocal length of the second lens element 20 is f2; the focal length ofthe third lens element 30 is f3; the focal length of the fourth lenselement 40 is f4; the focal length of the fifth lens element 50 is f5;the focal length of the sixth lens element 60 is f6; the refractiveindex of the first lens element 10 is n1; the refractive index of thesecond lens element 20 is n2; the refractive index of the third lenselement 30 is n3; the refractive index of the fourth lens element 40 isn4; the refractive index of the fifth lens element 50 is n5; therefractive index of the sixth lens element 60 is n6; the Abbe number ofthe first lens element 10 is ν1; the Abbe number of the second lenselement 20 is ν2; the Abbe number of the third lens element 30 is ν3;and the Abbe number of the fourth lens element 40 is ν4; the Abbe numberof the fifth lens element 50 is ν5; and the Abbe number of the sixthlens element 60 is ν6.

First Example

Please refer to FIG. 6 which illustrates the first example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 7A for the longitudinal spherical aberration on the image plane 71of the first example; please refer to FIG. 7B for the astigmatic fieldaberration on the sagittal direction; please refer to FIG. 7C for theastigmatic field aberration on the tangential direction, and pleaserefer to FIG. 7D for the distortion aberration. The Y axis of thespherical aberration in each example is “field of view” for 1.0. The Yaxis of the astigmatic field and the distortion in each example standsfor “image height”, which is 3.528 mm.

The optical imaging lens set 1 of the first example has six lenselements 10 to 60 with refractive power. The optical imaging lens set 1also has a filter 70, an aperture stop 80, and an image plane 71. Theaperture stop 80 is provided between the object side 2 and the firstlens element 10. The filter 70 may be used for preventing specificwavelength light (such as the infrared light) reaching the image planeto adversely affect the imaging quality.

The first lens element 10 has positive refractive power. The object-sidesurface 11 facing toward the object side 2 has a convex part 13 in thevicinity of the optical axis and a convex part 14 in a vicinity of itsperiphery. The image-side surface 12 facing toward the image side 3 hasa concave part 16 in the vicinity of the optical axis and a concave part17 in a vicinity of its periphery. Besides, the object-side surface 11is an aspherical surface.

The second lens element 20 has negative refractive power. Theobject-side surface 21 facing toward the object side 2 has a convex part23 in the vicinity of the optical axis and a convex part 24 in avicinity of its periphery. The image-side surface 22 facing toward theimage side 3 has a concave part 26 in the vicinity of the optical axisand a concave part 27 in a vicinity of its periphery. The image-side 22of the second lens element 20 is an aspherical surface. The first lenselement 10 and the second lens element 20 may be glued together so thereis no air gap between the image-side surface 12 of the first lenselement 10 and the object-side surface 21 of the second lens element 20to reduce the chance of flare.

The third lens element 30 has negative refractive power. The object-sidesurface 31 facing toward the object side 2 has a concave part 33 in thevicinity of the optical axis and a concave part 34 in a vicinity of itsperiphery. The image-side surface 32 facing toward the image side 3 hasa concave part 36 in the vicinity of the optical axis and a convex part37 in a vicinity of its periphery. Both the object-side surface 31 andthe image-side 32 of the third lens element 30 are aspherical surfaces.

The fourth lens element 40 has negative refractive power. Theobject-side surface 41 facing toward the object side 2 has a convex part43 in the vicinity of the optical axis and a concave part 44 in avicinity of its periphery. The image-side surface 42 facing toward theimage side 3 has a concave part 46 in the vicinity of the optical axisand a convex part 47 in a vicinity of its periphery. Both theobject-side surface 41 and the image-side 42 of the fourth lens element40 are aspherical surfaces.

The fifth lens element 50 has positive refractive power. The object-sidesurface 51 facing toward the object side 2 has a convex part 53 in thevicinity of the optical axis and a concave part 54 in a vicinity of itsperiphery. The image-side surface 52 facing toward the image side 3 hasa convex part 56 in the vicinity of the optical axis and a convex part57 in a vicinity of its periphery. Both the object-side surface 51 andthe image-side 52 of the fifth lens element 50 are aspherical surfaces.

The sixth lens element 60 has negative refractive power. The object-sidesurface 61 facing toward the object side 2 has a convex part 63 in thevicinity of the optical axis and a concave part 64 in a vicinity of itsperiphery. The image-side surface 62 facing toward the image side 3 hasa concave part 66 in the vicinity of the optical axis and a convex part67 in a vicinity of its periphery. Both the object-side surface 61 andthe image-side 62 of the sixth lens element 60 are aspherical surfaces.The filter 70 is disposed between the image-side 62 of the sixth lenselement 60 and the image plane 71.

In the first lens element 10, the second lens element 20, the third lenselement 30, the fourth lens element 40, the fifth lens element 50 andthe sixth lens element 60 of the optical imaging lens element 1 of thepresent invention, there are 12 surfaces, such as the object-sidesurfaces 11/21/31/41/51/61 and the image-side surfaces12/22/32/42/52/62. If a surface is aspherical, these asphericcoefficients are defined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}/\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}{a_{i} \times Y^{i}}}}$

In which:R represents the curvature radius of the lens element surface;Z represents the depth of an aspherical surface (the perpendiculardistance between the point of the aspherical surface at a distanceY from the optical axis and the tangent plane of the vertex on theoptical axis of the aspherical surface);Y represents a vertical distance from a point on the aspherical surfaceto the optical axis;K is a conic constant;a_(i) is the aspheric coefficient of the i^(th) order.

The optical data of the first example of the optical imaging lens set 1are shown in FIG. 22 while the aspheric surface data are shown in FIG.23. In the present examples of the optical imaging lens set, thef-number of the entire optical lens element system is Fno, EFL is theeffective focal length, HFOV stands for the half field of view which ishalf of the field of view of the entire optical lens element system, andthe unit for the curvature radius, the thickness and the focal length isin millimeters (mm). TTL is 5.5379 mm. Fno is 1.6689. The image heightis 3.528 mm. HFOV is 38.4693 degrees.

Second Example

Please refer to FIG. 8 which illustrates the second example of theoptical imaging lens set 1 of the present invention. It is noted thatfrom the second example to the following examples, in order to simplifythe figures, only the components different from what the first examplehas, and the basic lens elements will be labeled in figures. Othercomponents that are the same as what the first example has, such as theobject-side surface, the image-side surface, the part in a vicinity ofthe optical axis and the part in a vicinity of its periphery will beomitted in the following examples. Please refer to FIG. 9A for thelongitudinal spherical aberration on the image plane 71 of the secondexample, please refer to FIG. 9B for the astigmatic aberration on thesagittal direction, please refer to FIG. 9C for the astigmaticaberration on the tangential direction, and please refer to FIG. 9D forthe distortion aberration. The components in the second example aresimilar to those in the first example, but the optical data such as thecurvature radius, the refractive power, the lens thickness, the lensfocal length, the aspheric surface or the back focal length in thisexample are different from the optical data in the first example, and inthis example, image-side surface 32 facing toward the image side 3 ofthe third lens element 30 has a convex part 36′ in the vicinity of theoptical axis.

The optical data of the second example of the optical imaging lens setare shown in FIG. 24 while the aspheric surface data are shown in FIG.25. TTL is 5.4423 mm. Fno is 1.6661. The image height is 3.528 mm. HFOVis 38.2839 degrees. In particular, 1) the Fno of the second example issmaller than that of the first example of the present invention, 2) theimage quality of the second example is better than that of the firstexample of the present invention, and 3) the fabrication of the secondexample is easier than the first example so the yield is better.

Third Example

Please refer to FIG. 10 which illustrates the third example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 11A for the longitudinal spherical aberration on the image plane 71of the third example; please refer to FIG. 11B for the astigmaticaberration on the sagittal direction; please refer to FIG. 11C for theastigmatic aberration on the tangential direction, and please refer toFIG. 11D for the distortion aberration. The components in the thirdexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 51 facing toward the objectside 2 of the fifth lens element 50 has a concave part 53′ in thevicinity of the optical axis.

The optical data of the third example of the optical imaging lens setare shown in FIG. 26 while the aspheric surface data are shown in FIG.27. TTL is 5.4403 mm. Fno is 1.7302. The image height is 3.528 mm. HFOVis 38.9046 degrees. In particular, 1) the TTL of the third example isshorter than that of the first example of the present invention, 2) theHFOV of the third example is better than that of the first example ofthe present invention, 3) the image quality of the third example isbetter than that of the first example of the present invention, and 4)the fabrication of the third example is easier than the first example sothe yield is better.

Fourth Example

Please refer to FIG. 12 which illustrates the fourth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 13A for the longitudinal spherical aberration on the image plane 71of the fourth example; please refer to FIG. 13B for the astigmaticaberration on the sagittal direction; please refer to FIG. 13C for theastigmatic aberration on the tangential direction, and please refer toFIG. 13D for the distortion aberration. The components in the fourthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the aperture stop 80 is provided between the firstlens element 10 and the second lens element 20, the image-side surface32 facing toward the image side 3 of the third lens element 30 has aconvex part 36′ in the vicinity of the optical axis, the object-sidesurface 61 facing toward the object side 2 of the sixth lens element 60has a concave part 63′ in the vicinity of the optical axis. The aperturestop 80 provided between the first lens element 10 and the second lenselement 20 makes the field angle larger so the imaging quality isbetter.

The optical data of the fourth example of the optical imaging lens setare shown in FIG. 28 while the aspheric surface data are shown in FIG.29. TTL is 5.3949 mm. Fno is 1.8103. The image height is 3.528 mm. HFOVis 41.7104 degrees. In particular, 1) the TTL of the fourth example isshorter than that of the first example of the present invention, 2) thelocation of the aperture stop of the fourth example is different fromthat of the first example, 3) the image quality of the fourth example isbetter than that of the first example of the present invention, and 4)the fabrication of the fourth example is easier than the first exampleso the yield is better.

Fifth Example

Please refer to FIG. 14 which illustrates the fifth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 15A for the longitudinal spherical aberration on the image plane 71of the fifth example; please refer to FIG. 15B for the astigmaticaberration on the sagittal direction; please refer to FIG. 15C for theastigmatic aberration on the tangential direction, and please refer toFIG. 15D for the distortion aberration. The components in the fifthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 61 facing toward the objectside 2 of the sixth lens element 60 has a concave part 63′ in thevicinity of the optical axis.

The optical data of the fifth example of the optical imaging lens setare shown in FIG. 30 while the aspheric surface data are shown in FIG.31. TTL is 5.4151 mm. Fno is 1.7232. The image height is 3.528 mm. HFOVis 42.2274 degrees. In particular, 1) the TTL of the fifth example isshorter than that of the first example of the present invention, 2) theHFOV of the fifth example is better than that of the first example ofthe present invention, 3) the imaging quality of the fifth example isbetter than that of the first example of the present invention, and 4)the fabrication of the fifth example is easier than the first example sothe yield is better.

Sixth Example

Please refer to FIG. 16 which illustrates the sixth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 17A for the longitudinal spherical aberration on the image plane 71of the sixth example; please refer to FIG. 17B for the astigmaticaberration on the sagittal direction; please refer to FIG. 17C for theastigmatic aberration on the tangential direction, and please refer toFIG. 17D for the distortion aberration. The components in the sixthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the image-side surface 42 facing toward the imageside 3 of the fourth lens element 40 has a concave part 47′ in avicinity of its periphery and the object-side surface 61 facing towardthe object side 2 of the sixth lens element 60 has a concave part 63′ inthe vicinity of the optical axis.

The optical data of the sixth example of the optical imaging lens setare shown in FIG. 34 while the aspheric surface data are shown in FIG.35. TTL is 5.4975 mm. Fno is 1.72289. The image height is 3.528 mm. HFOVis 40.8937 degrees. In particular, 1) the TTL of the sixth example isshorter than that of the first example of the present invention, 2) theHFOV of the sixth example is better than that of the first example ofthe present invention, 3) the imaging quality of the sixth example isbetter than that of the first example of the present invention, and 4)the fabrication of the sixth example is easier than the first example sothe yield is better.

Seventh Example

Please refer to FIG. 18 which illustrates the seventh example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 19A for the longitudinal spherical aberration on the image plane 71of the seventh example; please refer to FIG. 19B for the astigmaticaberration on the sagittal direction; please refer to FIG. 19C for theastigmatic aberration on the tangential direction, and please refer toFIG. 19D for the distortion aberration. The components in the seventhexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 51 facing toward the objectside 2 of the fifth lens element 50 has a concave part 53′ in thevicinity of the optical axis and the object-side surface 61 facingtoward the object side 2 of the sixth lens element 60 has a concave part63′ in the vicinity of the optical axis.

The optical data of the seventh example of the optical imaging lens setare shown in FIG. 36 while the aspheric surface data are shown in FIG.37. TTL is 5.4927 mm. Fno is 1.7150. The image height is 3.528 mm. HFOVis 39.7529 degrees. In particular, 1) the HFOV of the seventh example isbetter than that of the first example of the present invention, 2) theimage quality of the seventh example is better than that of the firstexample of the present invention, and 3) the fabrication of the seventhexample is easier than the first example so the yield is better.

Eighth Example

Please refer to FIG. 20 which illustrates the eighth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 21A for the longitudinal spherical aberration on the image plane 71of the eighth example; please refer to FIG. 21B for the astigmaticaberration on the sagittal direction; please refer to FIG. 21C for theastigmatic aberration on the tangential direction, and please refer toFIG. 21D for the distortion aberration. The components in the eighthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the image-side surface 12 facing toward the imageside 3 of the first lens element 10 has a convex part 16′ in thevicinity of the optical axis and a convex part 17′ in a vicinity of itsperiphery, the object-side surface 21 facing toward the object side 2 ofthe second lens element 20 has a concave part 23′ in the vicinity of theoptical axis and a concave part 24′ in a vicinity of its periphery, theimage-side surface 32 facing toward the image side 3 of the third lenselement 30 has a convex part 36′ in the vicinity of the optical axis andthe object-side surface 51 facing toward the object side 2 of the fifthlens element 50 has a concave part 53′ in the vicinity of the opticalaxis.

The optical data of the eighth example of the optical imaging lens setare shown in FIG. 36 while the aspheric surface data are shown in FIG.37. TTL is 5.1147 mm. Fno is 1.3647. The image height is 3.528 mm. HFOVis 38.206 degrees. In particular, 1) the TTL of the eighth example isshorter than that of the first example of the present invention, 2) theFno of the eighth example is better than that of the first example ofthe present invention, and 3) the fabrication of the eighth example iseasier than the first example so the yield is better.

Some important ratios in each example are shown in FIG. 38. The distancebetween the image-side surface 62 of the sixth lens element 60 to thefilter 70 along the optical axis 4 is G6F; the thickness of the filter70 along the optical axis 4 is TF; the distance between the filter 70 tothe image plane 71 along the optical axis 4 is GFP; the distance betweenthe image-side surface 62 of the sixth lens element 60 and the imageplane 71 along the optical axis 4 is BFL. Therefore, BFL=G6F+TF+GFP.

In the light of the above examples, the inventors observe at least thefollowing features of the lens arrangement of the present invention andthe corresponding efficacy:

1. The third lens element has an object-side surface with a concaveportion in a vicinity of the optical axis, which facilitates thecorrection of the aberration of the first two optical imaging lenselements. When it goes with the sixth lens element which has animage-side surface with a convex portion in a vicinity of its periphery,they altogether further enhance the imaging quality of the opticalimaging lens set.2. The first lens element and the second lens element are glued togetherto render no air gap disposed between the first lens element and thesecond lens element to reduce flare.3. The satisfaction of the conditional formula |ν3−ν5|≤25, preferably0≤|ν3−ν5|≤25, reduces the dissatisfactory imaging quality cause byspherical aberration and by the chromatic aberration.

In addition, the inventors discover that there are some better ratioranges for different data according to the above various importantratios. Better ratio ranges help the designers to design a betteroptical performance and an effectively reduce length of a practicallypossible optical imaging lens set. For example:

To diminish the total length, the present invention proposes to reducethe lens thickness and air gaps between adjacent lens elements. Takingthe assembly fabrication and imaging quality into consideration, thelens thickness should suit air gaps. The following conditions help theoptical imaging lens set have better arrangement:

-   1. BFL/(G₃₄+G₅₆)≤8.1. Preferably, 0.1≤BFL/(G₃₄+G₅₆)≤8.1.-   2. AAG/G₅₆≤9.1. Preferably, 1.1≤AAG/G₅₆≤9.1.-   3. T₁/G₄₅≤6.6. Preferably, 1≤T₁/G₄₅≤6.6.-   4. ALT/T₆≤6.9. Preferably, 2.8≤ALT/T₆≤6.9.-   5. T₁/G₂₃≤2.2. Preferably, 0.2≤T₁/G₂₃≤2.2.-   6. BFL/T₆≤2.6. Preferably, 0.1≤BFL/T₆≤2.6.-   7. ALT/BFL≤3.5. Preferably, 0.5≤ALT/BFL≤3.5.

A smaller EFL helps enlarge the field angle so the EFL is preferablysmaller. The following conditions help the enlargement of the fieldangle in order to reduce the total length of the optical imaging lensset:

-   1. EFL/(G₃₄+G₅₆)≤42.3. Preferably, 5.2≤EFL/(G₃₄+G₅₆)≤42.3.-   2. EFL/T₆≤11.7. Preferably, 3.0≤EFL/T₆≤11.7.-   3. EFL/BFL≤4.9. Preferably, 2.1≤EFL/BFL≤4.9.-   4. EFL/G₂₃≤8.7. Preferably, 4.4≤EFL/G₂₃≤8.7.

The optical parameters and the total length of the optical imaging lensset together keep a suitable range so the parameters are not so great toenlarge the total length of the optical imaging lens set or too small tofabricate.

-   1. TTL/AAG≤6.1. Preferably, 1.5≤TTL/AAG≤6.1.-   2. TTL/TL≤1.4. Preferably, 0.9≤TTL/TL≤1.4.-   3. TL/T₄≤17.2. Preferably, 6.9≤TL/T₄≤17.2.

By limiting the optical parameters and the second lens element thicknessT₂, the second lens element thickness T₂ is not so large or so small tofacilitate the reduction of the optical aberration cause by the firstlens element.

-   1. T₃/T₂≤2.7. Preferably, 0.1≤T₃/T₂≤2.7.-   2. T₂/G₅₆≤1.8. Preferably, 0.1≤T₂/G₅₆≤1.8.

By limiting the fourth lens element thickness T₄ and other lens elementthickness or air gaps, the fourth lens element thickness T₄ is not solarge or so small to facilitate the reduction of the optical aberrationcause by the first lens element to the third lens element.

-   1. ALT/T₄≤13.1. Preferably, 4.6≤ALT/T₄≤13.1.-   2. T₆/T₄≤2.4. Preferably, 0.5≤T₆/T₄≤2.4.

By limiting the fifth lens element thickness T₅ and other lens elementthickness or air gaps, the fifth lens element thickness T₅ is not solarge or so small to facilitate the reduction of the optical aberrationcause by the first lens element to the fourth lens element.

-   1. T₅/(G₃₄+G₅₆)≤6. Preferably, 0.1≤T₅/(G₃₄+G₅₆)≤6.

Both the first lens element and the second lens element have sphericalsurfaces. They facilitate the easiness of the processing or thefabrication of the lens elements to promote higher production yields.

The gap disposed between the first lens element 10 and the second lenselement 20 may be filled with glue or with a film but it is not limitedto these so there is no air gap G₁₂ disposed between the first lenselement 10 and the second lens element 20.

In each one of the above examples, the longitudinal sphericalaberration, the astigmatic aberration and the distortion aberration meetrequirements in use. By observing three representative wavelengths ofred, green and blue, it is suggested that all curves of every wavelengthare close to one another, which reveals off-axis light of differentheights of every wavelength all concentrates on the image plane, anddeviations of every curve also reveal that off-axis light of differentheights are well controlled so the examples do improve the sphericalaberration, the astigmatic aberration and the distortion aberration. Inaddition, by observing the imaging quality data the distances amongstthe three representing different wavelengths are pretty close to oneanother, which means the present invention is able to concentrate lightof the three representing different wavelengths so that the aberrationis greatly improved. Given the above, the present invention providesoutstanding imaging quality.

Any one of the following conditions of the optical imaging lens setshows a smaller numerator when the denominator is fixed to exhibit thedecrease of the total size:

-   1. |ν3 −ν5|≤25.-   2. T₃/T₂≤2.7.-   3. EFL/(G₃₄+G₅₆)≤42.3.-   4. T₅/(G₃₄+G₅₆)≤6.-   5. BFL/(G₃₄+G₅₆)≤8.1.-   6. T₂/G₅₆≤1.8.-   7. AAG/G₅₆≤9.1.-   8. EFL/T₆≤11.7.-   9. T₁/G₄₅≤6.6.-   10. ALT/T₄≤13.1.-   11. EFL/BFL≤4.9.-   12. T₆/T₄≤2.4.-   13. TTL/AAG≤6.1.-   14. ALT/T₆≤6.9.-   15. T₁/G₂₃≤2.2.-   16. TTL/TL≤1.4.-   17. TL/T₄≤17.2.-   18. BFL/T₆≤2.6.-   19. ALT/BFL≤3.5.-   20. EFL/G₂₃≤8.7.

In the light of the unpredictability of the optical imaging lens set,the present invention suggests the above principles to have a shortertotal length of the optical imaging lens set, a larger apertureavailable, a wider field angle, better imaging quality or a betterfabrication yield to overcome the drawbacks of prior art. The abovelimitations may be properly combined at the discretion of persons whopractice the present invention and they are not limited as shown above.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical imaging lens set, from an object sidetoward an image side in order along an optical axis comprising: a firstlens element, a second lens element, a third lens element, a fourth lenselement, a fifth lens element and a sixth lens element, said first lenselement to said sixth lens element each having an object-side surfacefacing toward the object side as well as an image-side surface facingtoward the image side, wherein: no air gap between said first lenselement and said second lens element; said third lens element has anobject-side surface with a concave portion in a vicinity of said opticalaxis; and said sixth lens element has an image-side surface with aconvex portion in a vicinity of its periphery; the optical imaging lensset exclusively has six lens elements with refractive power, ν3 is anAbbe number of said third lens element and ν5 is an Abbe number of saidfifth lens element to satisfy |ν3−ν5|≤25.
 2. The optical imaging lensset of claim 1, wherein said second lens element has a second lenselement thickness T₂ along said optical axis and said third lens elementhas a third lens element thickness T₃ along said optical axis to satisfyT₃/T₂≤2.7.
 3. The optical imaging lens set of claim 1, wherein EFL is aneffective focal length of the optical imaging lens set, an air gap G₃₄between said third lens element and said fourth lens element along saidoptical axis and an air gap G₅₆ between said fifth lens element and saidsixth lens element along said optical axis to satisfyEFL/(G₃₄+G₅₆)≤42.3.
 4. The optical imaging lens set of claim 1, whereinsaid fifth lens element has a fifth lens element thickness T₅ along saidoptical axis, an air gap G₃₄ between said third lens element and saidfourth lens element along said optical axis and an air gap G₅₆ betweensaid fifth lens element and said sixth lens element along said opticalaxis to satisfy T₅/(G₃₄+G₅₆)≤6.
 5. The optical imaging lens set of claim1, wherein BFL is a distance between said image-side surface of saidsixth lens element and an image plane along said optical axis, an airgap G₃₄ between said third lens element and said fourth lens elementalong said optical axis and an air gap G₅₆ between said fifth lenselement and said sixth lens element along said optical axis to satisfyBFL/(G₃₄+G₅₆)≤8.1.
 6. The optical imaging lens set of claim 1, whereinsaid second lens element has a second lens element thickness T₂ alongsaid optical axis and an air gap G₅₆ between said fifth lens element andsaid sixth lens element along said optical axis to satisfy T₂/G₅₆≤1.8.7. The optical imaging lens set of claim 1, wherein a sum of all airgaps AAG between each lens elements from said first lens element to saidsixth lens element along said optical axis and an air gap G₅₆ betweensaid fifth lens element and said sixth lens element along said opticalaxis to satisfy AAG/G₅₆≤9.1.
 8. The optical imaging lens set of claim 1,wherein EFL is an effective focal length of the optical imaging lens setand said sixth lens element has a sixth lens element thickness T₆ alongsaid optical axis to satisfy EFL/T₆≤11.7.
 9. The optical imaging lensset of claim 1, wherein said first lens element has a first lens elementthickness T₁ along said optical axis and an air gap G₄₅ between saidfourth lens element and said fifth lens element along said optical axisto satisfy T₁/G₄₅≤6.6.
 10. The optical imaging lens set of claim 1,wherein ALT is a total thickness of all six lens elements and saidfourth lens element has a fourth lens element thickness T₄ along saidoptical axis to satisfy ALT/T₄≤13.1.
 11. The optical imaging lens set ofclaim 1, wherein EFL is an effective focal length of the optical imaginglens set and BFL is a distance between said image-side surface of saidsixth lens element and an image plane along said optical axis to satisfyEFL/BFL≤4.9.
 12. The optical imaging lens set of claim 1, wherein saidfourth lens element has a fourth lens element thickness T₄ along saidoptical axis and said sixth lens element has a sixth lens elementthickness T₆ along said optical axis to satisfy T₆/T₄≤2.4.
 13. Theoptical imaging lens set of claim 1, wherein AAG is a sum of all airgaps between each lens elements from said first lens element to saidsixth lens element along said optical axis and TTL is a distance fromsaid object-side surface of said first lens element to an image plane tosatisfy TTL/AAG≤6.1.
 14. The optical imaging lens set of claim 1,wherein ALT is a total thickness of all six lens elements and said sixthlens element has a sixth lens element thickness T₆ along said opticalaxis to satisfy ALT/T₆≤6.9.
 15. The optical imaging lens set of claim 1,wherein said first lens element has a first lens element thickness T₁along said optical axis and an air gap G₂₃ between said second lenselement and said third lens element along said optical axis to satisfyT₁/G₂₃≤2.2.
 16. The optical imaging lens set of claim 1, wherein TL is adistance between said object-side surface of said first lens element andsaid image-side surface of said sixth lens element along said opticalaxis and TTL is a distance from said object-side surface of said firstlens element to an image plane to satisfy TTL/TL≤1.4.
 17. The opticalimaging lens set of claim 1, wherein TL is a distance between saidobject-side surface of said first lens element and said image-sidesurface of said sixth lens element along said optical axis and saidfourth lens element has a fourth lens element thickness T₄ along saidoptical axis to satisfy TL/T₄≤17.2.
 18. The optical imaging lens set ofclaim 1, wherein BFL is a distance between said image-side surface ofsaid sixth lens element to an image plane along said optical axis andsaid sixth lens element has a sixth lens element thickness T₆ along saidoptical axis to satisfy BFL/T₆≤2.6.
 19. The optical imaging lens set ofclaim 1, wherein ALT is a total thickness of all six lens elements andBFL is a distance between said image-side surface of said sixth lenselement to an image plane along said optical axis to satisfyALT/BFL≤3.5.
 20. The optical imaging lens set of claim 1, wherein EFL isan effective focal length of the optical imaging lens set and an air gapG₂₃ between said second lens element and said third lens element alongsaid optical axis to satisfy EFL/G₂₃≤8.7.